We are studying, in vitro in isolated papillary muscles and in vivo in animals, the production of arrhythmias, myocardial contractile depression, and other kinds of cardiac toxicities by the fluorocarbon aerosol propellants. These cardiovascular toxic effects of the fluoroalkane propellants, which occur after their inhalation, may contribute to the sudden death of youths who deliberately inhale them and raise the possibility of harm to frequent aerosol users.